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incubator-nuttx/fs/vfs/fs_poll.c

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/****************************************************************************
* fs/vfs/fs_poll.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <poll.h>
#include <time.h>
#include <assert.h>
#include <errno.h>
#include <debug.h>
#include <nuttx/clock.h>
#include <nuttx/semaphore.h>
#include <nuttx/cancelpt.h>
#include <nuttx/fs/fs.h>
#include <nuttx/net/net.h>
#include <nuttx/tls.h>
#include <arch/irq.h>
#include "inode/inode.h"
/****************************************************************************
* Private Types
****************************************************************************/
struct pollfd_s
{
FAR struct pollfd *fds;
nfds_t nfds;
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: poll_setup
*
* Description:
* Setup the poll operation for each descriptor in the list.
*
****************************************************************************/
static inline int poll_setup(FAR struct pollfd *fds, nfds_t nfds,
FAR sem_t *sem)
{
unsigned int i;
unsigned int j;
int ret = OK;
/* Process each descriptor in the list */
for (i = 0; i < nfds; i++)
{
/* Setup the poll descriptor
*
* REVISIT: In a multi-threaded environment, one use case might be to
* share a single, array of struct pollfd in poll() calls on different
* threads. That use case is not supportable here because the non-
* standard internal fields get reset here on each call to poll()
* on each thread.
*/
fds[i].arg = sem;
fds[i].cb = poll_default_cb;
fds[i].revents = 0;
fds[i].priv = NULL;
/* Check for invalid descriptors. "If the value of fd is less than 0,
* events shall be ignored, and revents shall be set to 0 in that entry
* on return from poll()."
*
* NOTE: There is a potential problem here. If there is only one fd
* and if it is negative, then poll will hang. From my reading of the
* spec, that appears to be the correct behavior.
*/
if (fds[i].fd >= 0)
{
ret = poll_fdsetup(fds[i].fd, &fds[i], true);
}
if (ret < 0)
{
/* Setup failed for fds[i]. We now need to teardown previously
* setup fds[0 .. (i - 1)] to release allocated resources and
* to prevent memory corruption by access to freed/released 'fds'
* and 'sem'.
*/
for (j = 0; j < i; j++)
{
poll_fdsetup(fds[j].fd, &fds[j], false);
}
/* Indicate an error on the file descriptor */
fds[i].revents |= POLLERR;
return ret;
}
}
return OK;
}
/****************************************************************************
* Name: poll_teardown
*
* Description:
* Teardown the poll operation for each descriptor in the list and return
* the count of non-zero poll events.
*
****************************************************************************/
static inline int poll_teardown(FAR struct pollfd *fds, nfds_t nfds,
FAR int *count, int ret)
{
unsigned int i;
int status = OK;
/* Process each descriptor in the list */
*count = 0;
for (i = 0; i < nfds; i++)
{
if (fds[i].fd >= 0)
{
status = poll_fdsetup(fds[i].fd, &fds[i], false);
}
if (status < 0)
{
ret = status;
}
/* Check if any events were posted */
if (fds[i].revents != 0)
{
(*count)++;
}
/* Un-initialize the poll structure */
fds[i].arg = NULL;
fds[i].cb = NULL;
}
return ret;
}
/****************************************************************************
* Name: poll_cleanup
*
* Description:
* Cleanup the poll operation.
*
****************************************************************************/
static void poll_cleanup(FAR void *arg)
{
FAR struct pollfd_s *fdsinfo = (FAR struct pollfd_s *)arg;
int count;
poll_teardown(fdsinfo->fds, fdsinfo->nfds, &count, OK);
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: poll_fdsetup
*
* Description:
* Configure (or unconfigure) one file/socket descriptor for the poll
* operation. If fds and sem are non-null, then the poll is being setup.
* if fds and sem are NULL, then the poll is being torn down.
*
****************************************************************************/
int poll_fdsetup(int fd, FAR struct pollfd *fds, bool setup)
{
FAR struct file *filep;
int ret;
/* Get the file pointer corresponding to this file descriptor */
ret = fs_getfilep(fd, &filep);
if (ret < 0)
{
return ret;
}
DEBUGASSERT(filep != NULL);
/* Let file_poll() do the rest */
ret = file_poll(filep, fds, setup);
fs_putfilep(filep);
return ret;
}
/****************************************************************************
* Name: poll_default_cb
*
* Description:
* The default poll callback function, this function do the final step of
* poll notification.
*
* Input Parameters:
* fds - The fds
*
* Returned Value:
* None
*
****************************************************************************/
void poll_default_cb(FAR struct pollfd *fds)
{
int semcount = 0;
FAR sem_t *pollsem;
if (fds->arg != NULL)
{
pollsem = (FAR sem_t *)fds->arg;
nxsem_get_value(pollsem, &semcount);
if (semcount < 1)
{
nxsem_post(pollsem);
}
}
}
/****************************************************************************
* Name: poll_notify
*
* Description:
* Notify the poll, this function should be called by drivers to notify
* the caller the poll is ready.
*
* Input Parameters:
* afds - The fds array
* nfds - Number of fds array
* eventset - List of events to check for activity
*
* Returned Value:
* None
*
****************************************************************************/
void poll_notify(FAR struct pollfd **afds, int nfds, pollevent_t eventset)
{
int i;
FAR struct pollfd *fds;
DEBUGASSERT(afds != NULL && nfds >= 1);
for (i = 0; i < nfds && eventset; i++)
{
fds = afds[i];
if (fds != NULL)
{
/* The error event must be set in fds->revents */
fds->revents |= eventset & (fds->events | POLLERR | POLLHUP);
if ((fds->revents & (POLLERR | POLLHUP)) != 0)
{
/* Error or Hung up, clear POLLOUT event */
fds->revents &= ~POLLOUT;
}
if ((fds->revents != 0 || (fds->events & POLLALWAYS) != 0) &&
fds->cb != NULL)
{
finfo("Report events: %08" PRIx32 "\n", fds->revents);
fds->cb(fds);
}
}
}
}
/****************************************************************************
* Name: file_poll
*
* Description:
* Low-level poll operation based on struct file. This is used both to (1)
* support detached file, and also (2) by poll_fdsetup() to perform all
* normal operations on file descriptors.
*
* Input Parameters:
* file File structure instance
* fds - The structure describing the events to be monitored, OR NULL if
* this is a request to stop monitoring events.
* setup - true: Setup up the poll; false: Teardown the poll
*
* Returned Value:
* 0: Success; Negated errno on failure
*
****************************************************************************/
int file_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup)
{
FAR struct inode *inode;
int ret = -ENOSYS;
DEBUGASSERT(filep != NULL);
inode = filep->f_inode;
if (inode != NULL)
{
/* Is a driver registered? Does it support the poll method?
* If not, return -ENOSYS
*/
if ((INODE_IS_DRIVER(inode) || INODE_IS_MQUEUE(inode) ||
INODE_IS_SOCKET(inode) || INODE_IS_PIPE(inode)) &&
inode->u.i_ops != NULL && inode->u.i_ops->poll != NULL)
{
/* Yes, it does... Setup the poll */
ret = inode->u.i_ops->poll(filep, fds, setup);
if (ret < 0)
{
ferr("poll failed:%p, setup:%d, ret:%d\n",
inode->u.i_ops->poll, setup, ret);
}
}
#ifndef CONFIG_DISABLE_MOUNTPOINT
else if (INODE_IS_MOUNTPT(inode) && inode->u.i_mops != NULL &&
inode->u.i_mops->poll != NULL)
{
ret = inode->u.i_mops->poll(filep, fds, setup);
if (ret < 0)
{
ferr("poll failed:%p, setup:%d, ret:%d\n",
inode->u.i_ops->poll, setup, ret);
}
}
#endif
/* Regular files (and block devices) are always readable and
* writable. Open Group: "Regular files shall always poll TRUE for
* reading and writing."
*/
else if (INODE_IS_MOUNTPT(inode) || INODE_IS_BLOCK(inode) ||
INODE_IS_MTD(inode))
{
if (setup)
{
poll_notify(&fds, 1, POLLIN | POLLOUT);
}
ret = OK;
}
}
else
{
poll_notify(&fds, 1, POLLERR | POLLHUP);
ret = OK;
}
return ret;
}
/****************************************************************************
* Name: poll
*
* Description:
* poll() waits for one of a set of file descriptors to become ready to
* perform I/O. If none of the events requested (and no error) has
* occurred for any of the file descriptors, then poll() blocks until
* one of the events occurs.
*
* Input Parameters:
* fds - List of structures describing file descriptors to be monitored
* nfds - The number of entries in the list
* timeout - Specifies an upper limit on the time for which poll() will
* block in milliseconds. A negative value of timeout means an infinite
* timeout.
*
* Returned Value:
* On success, the number of structures that have non-zero revents fields.
* A value of 0 indicates that the call timed out and no file descriptors
* were ready. On error, -1 is returned, and errno is set appropriately:
*
* EBADF - An invalid file descriptor was given in one of the sets.
* EFAULT - The fds address is invalid
* EINTR - A signal occurred before any requested event.
* EINVAL - The nfds value exceeds a system limit.
* ENOMEM - There was no space to allocate internal data structures.
* ENOSYS - One or more of the drivers supporting the file descriptor
* does not support the poll method.
*
****************************************************************************/
int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout)
{
FAR struct pollfd *kfds;
sem_t sem;
int count = 0;
int ret2;
int ret;
DEBUGASSERT(nfds == 0 || fds != NULL);
/* poll() is a cancellation point */
enter_cancellation_point();
#ifdef CONFIG_BUILD_KERNEL
/* Allocate kernel memory for the fds */
kfds = kmm_malloc(nfds * sizeof(struct pollfd));
if (!kfds)
{
/* Out of memory */
ret = -ENOMEM;
goto out_with_cancelpt;
}
/* Copy the user fds to neutral kernel memory */
memcpy(kfds, fds, nfds * sizeof(struct pollfd));
#else
/* Can use the user fds directly */
kfds = fds;
#endif
/* Set up the poll structure */
nxsem_init(&sem, 0, 0);
ret = poll_setup(kfds, nfds, &sem);
if (ret >= 0)
{
struct pollfd_s fdsinfo;
/* Push a cancellation point onto the stack. This will be called if
* the thread is canceled.
*/
fdsinfo.fds = kfds;
fdsinfo.nfds = nfds;
tls_cleanup_push(tls_get_info(), poll_cleanup, &fdsinfo);
if (timeout == 0)
{
/* Poll returns immediately whether we have a poll event or not. */
ret = OK;
}
else if (timeout > 0)
{
/* "Implementations may place limitations on the granularity of
* timeout intervals. If the requested timeout interval requires
* a finer granularity than the implementation supports, the
* actual timeout interval will be rounded up to the next
* supported value." -- opengroup.org
*
* Round timeout up to next full tick.
*/
/* Either wait for either a poll event(s), for a signal to occur,
* or for the specified timeout to elapse with no event.
*
* NOTE: If a poll event is pending (i.e., the semaphore has
* already been incremented), nxsem_tickwait() will not wait, but
* will return immediately.
*/
ret = nxsem_tickwait(&sem, MSEC2TICK(timeout));
if (ret < 0)
{
if (ret == -ETIMEDOUT)
{
/* Return zero (OK) in the event of a timeout */
ret = OK;
}
/* EINTR is the only other error expected in normal operation */
}
}
else
{
/* Wait for the poll event or signal with no timeout */
ret = nxsem_wait(&sem);
}
/* Teardown the poll operation and get the count of events. Zero will
* be returned in the case of a timeout.
*
* Preserve ret, if negative, since it holds the result of the wait.
*/
ret2 = poll_teardown(kfds, nfds, &count, ret);
if (ret2 < 0 && ret >= 0)
{
ret = ret2;
}
/* Pop the cancellation point */
tls_cleanup_pop(tls_get_info(), 0);
}
nxsem_destroy(&sem);
#ifdef CONFIG_BUILD_KERNEL
/* Copy the events back to user */
if (ret == OK)
{
int i;
for (i = 0; i < nfds; i++)
{
fds[i].revents = kfds[i].revents;
}
}
/* Free the temporary buffer */
kmm_free(kfds);
out_with_cancelpt:
#endif
leave_cancellation_point();
if (ret < 0)
{
set_errno(-ret);
return ERROR;
}
else
{
return count;
}
}
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